J . Am. Chem. SOC.1985, 107, 405-409 sulfones 8b and 9b (878 mg, 2.47 mmol) in 4 mL of THF at -78 OC was added dropwise a solution of lithium diisopropylamide [prepared from diisopropylamine (494 pL, 357 mg, 3.50 mmol) and n-butyllithium (1.9 mL of a 1.55 M solution, 2.96 mmol) in 4 mL of THF]. An immediate intense red color was produced. This solution was allowed to warm to room temperature during 20 min, then recooled to -78 OC. To this solution was added neat methyl iodide (2 mL, 4.28 g, 30 mmol) whereupon most of the color was discharged. After reaction and workup as for the above case, the crude product was first purified by filtration through a short silica gel plug (5% ethyl acetate/hexane) to give the products in a 77/23 ratio as judged by IH N M R [signal for the major 1R*,5S* isomer 26b of 6 5.92 and signal for the minor isomer 27b at 6 5.761. Subsequent purification was performed by HPLC (2% ethyl acetate/hexane) to give two initial fractions containing 43 mg of the pure major 1R*,5S* isomer 26b and 590 mg of subsequent fractions containing mixtures of the two isomers (total product 633 mg, 69%). An analytical sample of the major 1R*,5S* isomer was obtained by recrystallization from hexane to give plates of mp 104-105 OC. IR (CHCI,): 1645, 1570, 1470, 1450, 1385, 1300, 1285, 1270, 1135 cm-'. 'H NMR (270 MHz, CDC13): 6 7.64 (4 H, m), 5.92 (1 H, br s), 4.70 (1 H, m), 4.62 (1 H, s), 2.60 (1 H, m), 2.25-1.70 (3 H, m), 2.01 (3 H, m), 1.65 (3 H, s), 1.50 (3 H, s), 1.40 (1 H, dd, J = 14.8, 13.6 Hz). MS, m / e (%): 150 ( 2 ) , 149 (39), 148 (4), 133 ( 5 ) , 121 (43), 108 (6), 107 (loo), 105 (9), 93 (16). 91 (6), 77 (6), 69 (12). Anal. Calcd for C,,H,,79Br02S: MW 368.0446; C, 55.28; H, 5.73; Br, 21.64; S, 8.68. Found: MW 367.9862; C, 55.46; H, 5.83; Br, 21.81; S, 8.61. (1R *,2R *,4S *)-2-Methyl-3-methylene-2-(phenylsulfonyl) bicyclo[2.2.l]hept-5-ene(31) and (1R*,2S*,4S*))-2-Methyl-3-methylene-2(phenylsulfonyl)bicyclo[2.2.l]hept-5-ene (30). To a solution of sulfone 28a" (176 mg, 0.72 mmol) in 4 mL T H F at -78 OC was added dropwise a solution of 1.6 M n-butyllithium (500 pL, 0.80 mmol). This mixture was stirred for 40 min at this temperature and then neat methyl iodide (500 pL, 1.14 g, 0.83 mmol) was added. This mixture was allowed to come to room temperature during 1 h and then partitioned between 60 mL of ether and 15 mL of 10% sodium bisulfate. The organic layer was then extracted with 200 mL of saturated sodium bicarbonate, separated, and dried, and the solvent was removed in vacuo. The crude product was judged to be a 77:32 mixture of sulfones 31 and 30 based on integration
405
of the 'H N M R [an olefinic signal at d 6.20 for 31 and at 6 6.31 for 301. The identity of the two isomers has been previously e~tab1ished.l~ The sulfone 28b15(178 mg, 0.72 mmol) was dissolved in 4 mL of THF and treated in a manner similar to that described above [also using n-butyllithium (500 pL, 0.80 mmol) and methyl iodide (500 pL, 1.14 g, 8.03 mmol)]. The crude alkylation product was judged to be a 77:23 mixture of 31 and 30,the same ratio as that obtained from 28a,so these crude products were combined and purified first by preparative TLC ( l / l , hexane/ethyl acetate) to give 282 mg (76%) of a mixture of 31 and 30. These two isomers were separated by preparative TLC using a freshly activated plate (baked at 110 OC for 2 h), and performing two elutions (5/1, hexane/ethyl acetate). This gave a mixture of 50 mg (13%) of 30 and 193 mg (52%) of 31 identified by a comparison of 'H N M R data with that previously r e p ~ r t e d . ' ~ (1R*,2R *,4S *)-2-Methyl-3-methylene-2-( phenylsulfonyl)-bicyclo[2.2.l]heptane (33)and (lR*,2S*,dS*)-2-MethyI-3-methylene-2-(phenylsulfonyl)bicyclo[2.2.l]heptane (32). To a solution of sulfone 29 (745 mg, 3.04 mmol) in 20 mL of T H F at -78 OC was added dropwise a solution of 1.6 M n-butyllithium (2.0 mL, 3.2 mmol). The solution at first becomes light yellow, then becomes dark red during 1 h (solution allowed to warm to -50 "C). The solution was recooled to -78 OC and neat methyl iodide was added. The solution was gradually allowed to warm. No fading of the intense red color was noted until the mixture reached a temperature of between -55 and -50 OC. The solution was pale yellow at -30 OC. After further warming to room temperature during 1 h, this mixture was partitioned between 50 mL of ether and 50 mL of brine. The organic layer was separated and dried, and the solvent was removed in vacuo to give a crude yellow solid. Purification was accomplished by chromatography on a silica gel column (ethyl acetate/hexane gradient) to give 718 mg (90%) of a mixture of sulfones 32 and 33 in an 81:19 ratio as determined by integration of 'H N M R [signal for 32 at 6 5.09 and for 33 at 6 5.141. This mixture was a solid of undetermined melting point. The identity of the two isomers was determined by comparison with the 'H NMR data reported by Veniard.15
Acknowledgment. W e thank the National Science Foundation and t h e General Medical Sciences Institute of the National Institutes of Health for their generous support of our programs.
Synthesis and X-ray Crystallographic Characterization of an Oxo-Bridged Bimetallic Organosamarium Complex, [ (C5Me5)2Sm 12(cL-o) William J. Evans,*lsVbJay W. Grate,lb Ira Bloom,lc William E. Hunter,ld and Jerry L. Atwood*ld Contribution from the Departments of Chemistry, The University of California, Iruine, Iruine, California 9271 7, The University of Chicago, Chicago, Illinois 60637, and The University of Alabama, University, Alabama 35486. Received May 17, 1984
.
Abstract: [(C5Me5)2Sm]2(p-O)is a common product in reactions of (C5Me5)2Sm(THF)2with oxygen-containing substrates such as NO, N,O, C H 3 C H 2 C H C H 2 0 or , C 5 H 5 N 0 . The epoxide reaction, which liberates CH3CH2CH=CH2 as a byproduct, gives the best yield, 55%. [(C5Me5)2Sm]2(p-O)crystallizes from toluene/hexane under pentane diffusion a t -3 OC in space group I42m with unit cell dimensions a = 11.560 (5) A, c = 14.236 (6) A, and Z = 2 (dimers) for 0,= 1.50 g cm-). Least-squares refinement on the basis of 962 observed reflections led to a final R value of 0.036. The two (C5Me5)2Smunits of the dimer are connected by a linear S m - G S m bridge with Sm-0 distances of 2.094 (1) A. The centroids of the four C5Me5rings define a tetrahedron which surrounds the Sm-0-Sm unit. The C5Me5 rings are in an eclipsed conformation on each samarium. In contrast to the above oxidation reactions, (C5Me5)2Sm(THF)2 reacts with OP(C6H5), to form the divalent adduct (CSM~S)~S~[~P(C~H,),I(THF).
T h e organometallic chemistry of t h e lanthanide metals in low oxidation states is currently undergoing rapid development. In-
0002-7863/85/ 1507-0405$01.50/0
vestigations of both zero-valent metal-vapor chemistry and divalent metal-complex chemistry have led to a variety of new classes of
0 1985 American Chemical Society
406 J . Am. Chem. SOC.,Vol. 107, No. 2, 1985 complexes and reactivity patterns.2-’0 In the divalent area, only three of the lanthanide elements, Eu, Yb, and S m , have 2+ oxidation states accessible under normal chemical conditions. Of these, samarium is the most reactive, both because it is the strongest reducing agent” and because it is the largest of these metals, which means its complexes are often coordinatively less saturated and less stable.I2 As part of our general investigation of low-valent lanthanide ~hemistry,”~we have recently synthesized and structurally characterized the first soluble organosamarium(I1) complex, ( C , M e s ) 2 S m ( T H F ) 2 (I).3 As expected, this complex is highly reactive with a wide range of substrates3 and it has also allowed the preparation of the most active f-element based catalysts for activation of hydrogen, [ ( C 5 M e S ) 2 S m ] 2 ( C 6 H 5 ) 2 C(II), 2 and [(C,MeS)2SmH]2 Given the high reactivity of Sm(I1) and t h e g r e a t oxophilicity of t h e l a n t h a n i d e s in general, (C5Me5)2Sm(THF)2is also very reactive with oxygen-containing substrates. W e report here the synthesis a n d crystal structure of a bridged trivalent oxide complex, (C,Mes)2Sm-O-Sm(C,Me5)2 (IV), which is a product in several of these reactions. Organometallic oxide complexes are rare in f-element chemistry and only in the actinide area have examples been briefly mentioned. [ ( C , H s ) , U ] 2 0 has been reported in a reviewI3 and (CSMes)-U-O units have been postulated as intermediates during the preparation of heterogeneous catalytic systems derived from organoactinide complexes deposited on aluminum oxide supports.I4 Since lanthanide oxygen bonds are very strong and since in the largely ionic lanthanide complexes oxide ligands may be compatible with reactive alkyl and hydride functionalities, a Ln-O-Ln unit may provide a stable framework on which to build reactive organometallic complexes. In addition to their intrinsic worth, such complexes may be of interest with respect to the oxidesupported heterogeneous organometallic catalysts and to lan( I ) (a) Alfred P. Sloan Research Fellow. (b) University of California, Irvine. (c) University of Chicago. (d) University of Alabama. (2) (a) Evans, W. J.; Engerer, S. C.; Neville, A. C. J . Am. Chem. SOC. 1978, 100, 331-333. (b) Evans, W. J.; Wayda, A. L.; Chang, C. W.; Cwirla, W. M. J . A m . Chem. SOC.1978, 100, 333-334. (c) Zinnen, H. A,; Evans, W. J.; Pluth, J. J. JChem. Soc., Chem. Commun. 1980, 81C-812. (d) Evans, W. J.; Engerer, S. C.; Piliero, P. A,; Wayda, A. L. J . Chem. SOC.,Chem. Commun. 1979, 1007-1008. (e) Evans, W. J.; Engerer, S . C.; Piliero, P. A.; Wayda, A. L. “Fundamentals of Homogeneous Catalysis”; Tsutsui, M., Ed.; Plenum Publishing Corp.: New York, 1979; Vol. 3, pp 941-952. (f) Evans, W. J.; Engerer, S. C.; Coleson, K. M. J . Am. Chem. SOC.1981, 103, 6672-6677. (g) Evans, W. J.; Coleson, K. M.; Engerer, S . C. Inorg. Chem. 1981, 20, 4115-4119. (h) Evans, W. J. In “The Rare Earths in Modern Science and Technology”; McCarthy, G. J., Rhyne, J. J., Silber, H. E., Eds.; Plenum Press: New York, 1982; Vol. 3, pp 61-70. (i) Evans, W. J. J . Organomet. Chem. 1983, 250, 217-226. (j)Evans, W. J.; Bloom, I.; Engerer, S . C. J . Catal. 1982, 104, 2008-2014. (3) Evans, W. J.; Bloom, I.; Hunter, W. E.; Atwood, J. L. J . Am. Chem. SOC.1981, 103, 6507-6508. (4) Evans, W. J.; Bloom, I.; Hunter, W. E.; Atwood, J. L. J . Am. Chem. SOC.1983, 105, 1401-1403. (5) Evans, W. J.; Hughes, L. A.; Hanusa, T. P. J . Am. Chem. SOC.1984, 106, 4270-4272. (6) Watson, P. L. J . Chem. Soc., Chem. Commun. 1980, 652-653. (7) (a) Tilley, T. D.; Andersen, R. A,; Spencer, B.; Ruben, H.; Zalkin, A,; Templeton, D. H. Inorg. Chem. 1980, 19, 2999-3003. (b) Tilley, T. D.; Andersen, R. A. J . Am. Chem. SOC.1982,104, 1772-1774. (c) Tilley, T. D.; Andersen, R. A,; Zalkin, A. J . Am. Chem. SOC.1982, 104, 3725-3727. (d) Boncella, J. M.; Andersen, R. A. Inorg. Chem. 1984, 23, 432-437. (8) Lappert, M. F.; Yarrow, P. I. W.; Atwood, J. L.; Shakir, R.; Holton, J. J . Chem. SOC.,Chem. Commun. 1980, 987-988. (9) Deacon, G. B.; Koplick, A. J.; Raverty, W. D.; Vince, D. G. J . Organomet. Chem. 1979, 182, 121-141 and references therein. ( I O ) Girard, P.; Namy, J. L.; Kagan, H. B. J. Am. Chem. SOC.1980, 102, 2693-2698. (1 1) The Sm3+/Sm2+reduction potential is -1.5 V vs. NHE: Morss, L. R. Chem. Rev. 1916, 76, 827-841. (12) (a) Evans, W. J. In ‘The Chemistry of the Metal-Carbon Bond”; Hartley, F. R., Patai, S., Eds.; John Wiley: New York, 1982; Chapter 12, pp 489-537. (b) Marks, T. J.; Ernst, R. D. In ’Comprehensive Organometallic Chemistry”; Wilkinson, G., Stone, F. G. A,, Abel, E. W., Eds.; Pergamon Press: Oxford, 1982; Chapter 21. (e) Evans, W. J. Adu. Urganomet. Chem., in press. (13) Baumgartner, F.; Fischer, E. 0.;Kanellakopulos, B., unpublished results reported in: Marks, T. J., Fischer, R. D., Eds. “Organometallics of the f-Elements”; D. Reidel Publishing Co.: Dordrecht, Holland, 1979; pp 1-35. (14) He, M.-Y.; Burwell, R. L., Jr.; Marks, T. J. Organometallics 1983, 2, 566-569.
Euans et al.
wMel
Me2
Figure 1. Molecular structure of [(CSMes),Sm],(p-O) with samarium atoms darkened.
Table I. Bond Lengths (A) and Angles (deg) for I(CsMesMmldrr-O) atoms distance atoms distance Sm-Sm 4.189 ( I ) Sm-0 2.094 (1) Sm-Cp( 1) 2.72 (1) Sm-Cp(2) 2.73 ( I ) Sm-Cp(3) 2.77 (1) Sm-Cnt(l) 2.470 Cp(l)-Cp(2) 1.42 ( I ) Cp(l)-Me(1) 1.54 (2) Cp(2)-Cp(3) 1.42 (1) Cp(2)-Me(2) 1.55 (2) Cp(3)-Cp(3)’ 1.38 (2) Cp(3)-Me(3) 1.50 (2) atoms angle atoms angle Cnt(1)-Sm-Cnt(1) 137.177 0-Sm-Cnt(1) 111.412 Sm-0-Sm 107.6 (9) 180.000 Cp(2)-Cp(l)-Cp(2)’ 107.5 (9) Cp(2)-Cp(1)-Me(1) 126.1 (6) Cp(l)-Cp(2)-Cp(3) 125 (1) Cp(l)-Cp(2)-Me(2) 128 (1) Cp(3)-Cp(2)-Me(2) 127 (1) Cp(2)-Cp(3)-Cp(3)’ 108.6 (8) Cp(2)-Cp(3)-Me(3) thanide oxide containing catalysts. This report describes how divalent lanthanide complexes can be used to provide a direct route to a trivalent bimetallic organolanthanide oxide complex prototype.
Results and Discussion Reactions of (CjMe5)2Sm(THF)2Leading to [(CjMe5)2Sm],( p - 0 ) . [(CsMe,)2Sm]2(p-O)(IV) was first obtained while surveying the reactivity of ( C 5 M e 5 ) 2 S m ( T H F ) 2(I) with a variety of small molecule^.^ In the reaction with N O , purple solutions of I were rapidly oxidized to give orange solutions containing mixtures of trivalent products. Varying the reaction conditions and stoichiometry failed to simplify the complex distribution of products, but a toluene-soluble yellow product was consistently formed and could be. isolated. Recrystallization gave single crystals which were identified as IV by X-ray crystallography. The ‘ H N M R spectrum of IV consists of a characteristic singlet a t 0.06 ppm, allowing it to be conveniently identified when it is formed in other reactions. N20,a reagent used to prepare bridging oxo complexes of transition metals,lsJ6 also yields IV on reaction with I. Desolvation of I a t 75-125 “ C under vacuum, a reaction which results primarily in the sublimation of ( C 5 M e J 2 S m (V),j also forms small amounts of IV. In this case, the bridging oxygen atom would appear to be derived from T H F . IV is also observed as a minor product in reactions of a variety of (C,MeS)2SmZ systems such as [(C,Me5)2SmH]2,4[(CSMeS)2Sm]2C2(C6HS)~,4 and (C5Me5)2Sm(C6H5)(THF)’7 if any trace amount of a reactive oxygen-containing material is available. These divalent and trivalent organosamarium compounds are so reactive that the absence of IV in reaction solutions provides a very sensitive indication that no contamination by oxygen-containing species has occurred. (15) Bottomley, F.; Brintzinger, H. H. J . Chem. Soc., Chem. Commun.
1978, 234-235.
(16) Bottomley, F.; White, P. S. J . Chem. SOC.,Chem. Commun. 1981, 28-29. Bottomley, F.; Lin, I . J. B. J . Chem. Soc., Dalton Trans. 1981, 27 1-275. (17) Evans, W. J.; Bloom, I.; Hunter, W. E.; Atwood, J. L. Organometallics, in press.
J . Am. Chem. SOC.,Vol. 107. No. 2, 1985 407
Synthesis of ((C,MeJ,Sm],(cc- 0) Table 11. Bond Distances ~~~~~
and Aneles (dee) in Oxo-Brideed Earlv Transition Metal and Lanthanide Comolexes ~
~
~
(1)
complex [CJLTiCI,l(wc-O) iTikliacacj;] 2 ( p - 0 ) (CHCI3)
M-0 distance 1.777 (1) 1.79 (2) 1.81 (2) 1.798 (0) 2.094 (1) 1.825 (2) 1.829 (2) 1.834 1.837 (2) 1.910 (6)
angle 180 167.5 (11) 180 180 178.1 (8) 175.8 (5) 177.0 173.8 132.5 (8) 170.0 (2) 173.9 (3) 144 (2) 168.9 (8)
1.856 (6) 1.941 (3) 1.95 (2) 1.94 ( I ) 1.95 (1) 174.1 (3) 1.948 (1) 1.950 (1) 180 142.5 (2) 1.950 (6)1.9665 (0) 169.3 (8) 1.88 (1) 180 1.926 (2) 165.8 (2) 1.964 (3) 1.968 (3) 171.8 (1) 1.901 (2) 1.926 (2) “Reference 22. bReference 42. c i 0 . 0 2 . Estimated from ref 22 and 42.
Preparative Scale Syntheses of IV. Since IV may prove to be a n interesting starting material for mixed organometallic-oxide chemistry, we were interested in developing a synthesis for it that was higher in yield and cleaner in product purity and isolation procedure than the complex reactions discussed above. Among the reagents surveyed were pyridine N-oxide and 1,2-epoxybutane. Pyridine N-oxide is a convenient solid reagent, yielding IV as a microcrystalline yellow powder in 47% yield (eq 1). 1,2-EpH
H
2(C5Me5)2Sm(THF)2
(11
C(C,Me,),Sml,(p-O)
oxybutane, a liquid, is also easy to handle and yields IV in 5 5 % yield (eq 2). The byproduct of reaction 2, 1-butene, was identified
2(C5Me5)2Sm(THF)2
+
/ \
CH2-CHCH2CH3
C(C,Me,),Sml,(p-O)
-I-4THF (2)
-k CH,=CHCH,CH,
by gas chromatography. Solutions of SmI, in THF a r e known to convert epoxides to alkenes, but the nature of the samariumcontaining product was not investigated.’O Reaction of I with (C,H,),PO. Addition of a solution of (C,H,),PO in toluene to a purple solution of I in toluene does not yield either IV or a product with the pale yellow-orange color characteristic of Sm(II1) complexes. On standing, black crystals were obtained which were identified a s the divalent complex (C5Me5),Sm[OP(c6H5),](THF) by ‘H N M R spectroscopy, I R spectroscopy, magnetic moment measurement, and complete elemental analysis. Although ( C 6 H 5 ) 3 P 0 has been used to advantage as a coordinating base in actinide chemistry,’* its use with organolanthanides has been limited until r e ~ e n t l y . l ~ * ~ ~ ~~
~
~
~~~
(18) Bagnall, K . W.; Lopez, 0. V.; Xing-fu, L. J . Chem. SOC.,Dalton Trans. 1983, 1153-1 158 and references therein. (19) This work and: Evans, W. J.; Grate, J. W. “Industrial Associates Conference on Recent Trends in Heterogeneous and Homogeneous Catalysis”; California Institute of Technology, March 21-23, 1984.
(2) general M radius” 0.68 0.68 0.68 0.68 0.964 0.68 0.68 0.68 0.68 0.74 0.68 0.75 0.75 0.74 0.74 0.74 0.74 0.74 0.74 0.66‘ 0.7Ie 0.74 0.74 0.66c 0.66
